CFCs and the Atmosphere
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CFCs and ozone loss
Annual average ozone levels over southern Australia have declined by about 4% (Brisbane) to 9% (Hobart) over the past 20 years. Annual average polar ozone losses exceed 20%.
The amount of UV radiation that reaches southern Australia is, in part, controlled by the amount of ozone in the atmosphere. If the other factors that control UV levels over Australia (average cloud cover and particulate loadings) have not changed, then UV-B levels that cause skin cancer are calculated to have increased by 6% (Brisbane) to 14% (Hobart).
The causes of this significant ozone loss, both over southern Australia and the polar regions, are the growing levels of chlorine and bromine in the upper atmosphere (stratosphere). Combined chlorine and bromine levels have increased by 150% over the past 20 years.
This chlorine has reached the stratosphere via CFCs (chlorofluorocarbons) and certain chlorinated solvents (those that survive long enough in the atmosphere to reach the stratosphere) from refrigeration/air conditioning systems, foam plastics, aerosol products and surface cleaning processes. The bromine comes from halons in fire fighting equipment and methyl bromide used in agriculture.
The Montreal Protocol (1987)
Australia is a signatory to the Montreal Protocol (1987) and its subsequent adjustments and amendments. The Protocol is an international agreement which requires the complete phase out of the production and import of halons by 1994, CFCs and the long-lived chlorinated solvents by 1996 and methyl bromide, with some exceptions, by 2010.To comply with the Montreal Protocol, industry has had to develop and implement the use of several interim and long term replacements for CFCs.
HFAs, sometimes referred to HFCs (hydrofluorocarbons) are the preferred replacements because they contain neither chlorine nor bromine and therefore have no detrimental effect on stratospheric ozone. The most widely used HFA is HFA-134a which has only one third of the ‘greenhouse’ (global warming) effect of the CFCs it replaces. Thus the conversation of industries from CFC use to HFA use has reduced and will reduce both stratospheric ozone depletion and global warming.
CFC accumulation declining
As a result of global compliance to the Montreal Protocol several years ahead of the mandated schedule, the accumulation of CFCs, long-lived chlorinated solvents and halons in the atmosphere has either slowed significantly, stopped or actually started to decline. This means that the maximum loss of stratospheric ozone will occur over the next few years (probably before 2000) and subsequently global ozone levels will begin to slowly recover.
Significant evidence of global ozone recovery is expected between 2005 and 2010
CFCs in Australia
CFC consumption in Australia peaked in the mid-1970s at around 20,000 tonnes per year, largely from the aerosol, refrigeration and foam plastics industries. By the end of the 1980s the aerosol industry had virtually stopped using CFCs, but growing consumption by the other major users meant that around 10,000 tonnes per year of CFCs were still being used. Adoption of a national strategy, guided by the Montreal Protocol, to protect the ozone layer, has resulted in CFC consumption in Australia dropping dramatically to less than 2,000 tonnes of CFCs per year, i.e. about 10-15% of Australia’s consumption.
Historically, asthma aerosol inhalers have released less than 1% of the estimated half a million tonnes of CFCs released by all industries in Australia since the inception of their use in the 1960s.